In the new study, the team focused on neurons called amacrine cells and horizontal cells, which have a known role in adjusting electrical signals transmitted to the brain from the photoreceptors after they have been stimulated by light photons.These cells first caught the researchers' attention because they appear to wrap themselves around the blood vessels (all together called the vasculature) of the intermediate layer.

They found that these mice never developed normal blood vessels in the intermediate layer, leading to degeneration of the photoreceptors and severe vision impairment."This was surprising since previous research had given no clues that these cells were an important source of VEGF," said research associate Peter Westenskow, co-first author of the paper.This provides evidence that VEGF from the amacrine and horizontal cells really does make a difference in blood vessel growth."This is fascinating. The signals from these cells are fine-tuning this layer of the vasculature," the authors noted.The study was published in The Journal of Clinical Investigation.